Well i think magma moving nearby santorini and best of all would be some kind of little eruption nearby. But i think santroini is started building its magma chamber and there will quite much that magma stuff. I mean there could be huge magma deposit beneath santorini and now it goming up and generates new magma chamber wich one will erupt. There is now quite long time when it last time erupt.

Anyway there was good article wich told that even small eruption here can cause that tsunami and collapsing in caldera because it is empty and land is so weak it collapsed and make erution lots of chatastropical that it should be.